issue #71 - Added provision for compound scheduling in experiment creation flow.  Need to update the backend (specifically, saving the ExperimentDAO to the datastore) to support this.
issue #127 - modified creation flow to guarantee that default feedback, publishing, and duration are set on the experiment.
issue #71 - Added SignalMechanismChooserListPanel to commit. Necessary in compound-scheduling frontend.
issue #127 - Fixed null pointer exception in ExperimentDAOCore end date validation.
issue #127 - Fixed some verification errors with experiment start and end dates.
Merge branch 'issue127' into newCreationFlow
Merge branch 'multiSignalGroupFrontend' into newCreationFlow
issue #71 - Fixed problem with previous and next buttons caused by un-edited instanceof expression when moving from SignalMechanismChooserPanel to SignalMechanismChooserListPanel structure.